1. Field
The following description relates generally to wireless communication and, more particularly, to device discovery on white space frequencies.
2. Background
White space refers to frequency spectrum that is not used by any licensed technology/primary user in many geographical locations. In the absence of a primary user, this frequency spectrum is available for use by any other user (i.e., secondary user) using any technology. A communication network over white space frequencies (or cognitive frequencies) is fundamentally different from more traditional deployments because the same frequency (or channel) may not be available at all locations because of the presence of a primary user (such as TV signal or a wireless microphone), and the same channel is shared by various devices using disparate technologies creating an interference pattern that changes spatially and temporally.
The unavailability of the same white space frequency and changes in the interference pattern compels a device in a wireless communication network, also called a network node, to select a frequency that is locally available and observes less interference from other devices. In a multipoint network, multiple receive nodes want to communicate with each other over the same wireless link, while in a point-to-point network, a transmit node wants to communicate with a specific receive node over the wireless link. The network nodes may use a certain negotiation protocol to select a frequency of communication. For example, in a point-to-point scenario, a receive node may broadcast a signature on the frequency the receive node has selected. After detecting the signature, the transmit node can either start communicating with the receive node on frequency selected by the receive node or invite the receive node to join the conversation at some other frequency. In a multipoint network, a node, acting as a group leader, can invite the other nodes to join the conversation at a frequency suitable for all nodes in the multipoint network.
The problem with such negotiation protocols is that while they are suitable for initialization and during power on, they are slow in scenarios where network nodes frequently change the communication group within a network, due to mobility, service change or otherwise. Each node has to scan through all available white space frequencies to detect the frequency on which the node can communicate with one node of a new group of nodes. Scanning through the available white space frequencies is impractical or inefficient. As such, there is a need in the art for an efficient method of device discovery on white space frequencies.